Magnetic configuration for Faraday rotators

Abstract

A Faraday rotator having an optical element and a donut magnet of length 1.0L for generating a magnetic field along the optical axis of the optical element in order to rotate a plane of polarization of polarized light. At each end of the donut magnet of length 1.0L is a tuning magent of a length from about 0.4L to about 0.7L, with each of said tuning magnets generating a magnetic field in a direction opposite to that of the donut magnet.

What is claimed is: 
     
       1. A Faraday rotator comprising: an optical element having an optical axis, said optical element being made of a light transmitting material;   a first magnet for generating a magnetic field along the optical axis of said optical element, said magnet having a front end and a rear end, said magnetic field being generated in one direction and said first magnet having a specified length 1.0L; and   a pair of tuning magnets, each tuning magnet being located at a front end or a rear end of said first magnet, each tuning magnet generating a magnetic field in a direction opposite to the direction of the magnetic field being generated by said first magnet, and the total combined length of said tuning magnets being from about 0.8L to about 1.4L.   
     
     
       2. The Faraday rotator of claim 1 wherin each of said tuning magnets has a length of from about 0.4L to about 0.7L. 
     
     
       3. The Faraday rotator of claim 2 wherein each of said tuning magnets has a specified length 1/2 L. 
     
     
       4. The Faraday rotator of claim 1 wherein each of said tuning magnets is a permanent magnet. 
     
     
       5. The Faraday rotator of claim 4 wherein each of said tuning magnets is a permanent magnet made of a material containing samarium and cobalt. 
     
     
       6. The Faraday rotator of claim 4 wherein each of said tuning magnets is a permanent magnet made of a material containing neodymium, iron, and boron. 
     
     
       7. An optical isolator comprising: an input polarizer or polarizing beams or waves of light;   a Faraday rotator, said Faraday rotator comprising:   an optical element having an optical axis, said optical element being made of a light transmitting material;   a first magnet for generating a magnetic field along the optical axis of said optical element, said magnet having a front end and a rear end, said magnetic field being generated in one direction and said first magnet having a specified length 1.0L; and   a pair of tuning magnets, each tuning magnet being located at a front end or a rear end of said first magnet, each tuning magnet generating a magnetic field in a direction opposite to the direction of the magnetic field being generated by said first magnet, and the total combined length of said tuning magnets being from about 0.8L to about 1.4L; and   an output polarizer.   
     
     
       8. The optical isolator of claim 7 wherein each of said tuning magnets has a length of from about 0.4L to about 0.7L. 
     
     
       9. The optical isolator of claim 8 wherein each of said tuning magnets has a specified length 1/2 L. 
     
     
       10. The optical isolator of claim 7 wherein each of said tuning magnets is a permanent magnet. 
     
     
       11. The optical isolator of claim 10 wherein each of said tuning magnets is a permanent magnet made of a material containing samarium and cobalt. 
     
     
       12. The optical isolator of claim 10 wherein each of said tuning magnets is a permanent magnet made of a material containing neodymium, iron, and boron.